Major related issue fixed in r15783.
This fixes a number of codecs which are now parsed correctly, so r15784 removes them from the blacklist: aac and mp3 via the media source API. (and maybe this should only be done if the server exposes a flag to state that it won't send broken streams since those can crash Safari..)
Sadly, this doesn't fix software decoding via aurora. (so those codecs remain disabled there)

Related: we now handle IE sound using an http stream (r15781 + r15782)